This invention relates to polydiorganosiloxane oligourea segmented copolymers and a process for making same.
Polydiorganosiloxane polymers have unique properties derived mainly from the physical and chemical characteristics of the siloxane bond. Typically, the outstanding properties of polydiorganosiloxane polymers include resistance to ultraviolet light, extremely low glass transition temperature, good thermal and oxidative stability, good permeability to many gases, very low surface energy, low index of refraction, good hydrophobicity, and good dielectric properties. They also have very good biocompatability and are of great interest as biomaterials that can be used in the body in the presence of blood. Polydiorganosiloxane elastomers have been widely used because of these many excellent properties. But, their limited tear resistance and poor resistance to low polarity solvents have made them unsuitable in many other applications.
Elastomers possess the ability to recover their initial shape from deformation produced by an imposed force. Traditional polydiorganosiloxanes show elastomeric behavior only when they are chemically or physically crosslinked. Even extremely high molecular weight polydiorganosiloxane gums (greater than 500,000 grams per mole) exhibit cold flow when uncrosslinked. However, chemical crosslinking results in polymers with poor mechanical properties relative to other organic materials. Thus, to be useful in most commercial applications, traditional polydiorganosiloxanes must be further filled with up to 50 weight percent fillers such as finely divided high surface area silica, fumed silica, titanium dioxide, alumina, zirconia, pigment-grade oxides, carbon blacks, graphite, metal powders, clays, calcium carbonates, silicates, aluminates, fibrous fillers, and hollow glass or plastic microspheres, depending on the desired properties, for example, to maintain their mechanical strength and reduce swelling in solvents. Since polydiorganosiloxanes do not lose their mechanical strength as abruptly as other organic materials at elevated temperatures, they find particular use in high temperature applications.
For many uses such as in insulated wire, rods, channels, tubing, and similar products, polydiorganosiloxane compounds are extruded in standard rubber extrusion equipment. The extruded material must immediately be heated to set the form. Usually, hot-air vulcanization at 300-450xc2x0 C. or steam at 0.28-0.70 MPa (40-100 psi) for several minutes is needed. Final properties can be developed by oven curing or by continuous steam vulcanization.
For many other uses such as in elastomers, caulking, gaskets, sealants, and release coatings, polydiorganosiloxane compounds are applied as liquids or deformable semi-solids at room temperature and require intimate mixing if two part systems are used. Final properties are developed after lengthy cure times and are generally inferior. Often a delay occurs before the next sequence in manufacture or repair can proceed.
In recent years, free radically cured and moisture cured liquid polydiorganosiloxane compositions have been disclosed that cure rapidly and completely under exposure to radiation or moderately elevated temperatures with excellent properties. Thus, subsequent manufacturing or repair steps are often delayed until some degree of curing occurs. Also, thick constructions cannot be made without temporary support until curing is accomplished and irregularly shaped surfaces can be difficult to coat adequately. Therefore, there is still a need for polydiorganosiloxane compositions with green strength, i.e., strength in the uncured state, and controlled flow properties.
Silicone-based release coatings have been used commercially for some time, predominantly in such applications as release liners for adhesives. Generally, these materials are coated from solvent or a carrier and thermally crosslinked at high temperatures. Recently, silicone release technologies have been disclosed that include addition cure, cationic cure, radiation cure, and moisture cure of monomer, oligomer or polymer systems as well as silicone-containing block copolymers that do not require curing. Some of these systems can be coated without solvent, e.g., by roll coating. Others can be coated from organic solvents or water. There is still a need for a silicone-based coating with controlled flow properties and good green strength while retaining the desirable release performance features of the previously mentioned materials.
Physically crosslinked polydiorganosiloxane polyurea segmented copolymers, that may contain blocks other than polydiorganosiloxane or urea, are elastomers that are synthesized in and coated out of solvent. These copolymers have some potential process economy advantages because their synthesis reaction is rapid, requires no catalyst, and produces no by-products.
In producing polydiorganosiloxane polyurea segmented copolymers, monofunctional reaction impurities in the polydiorganosiloxane diamine precursor can inhibit the chain extension reaction and limit the attainment of optimum molecular weight and tensile strength of the polymer. Because the early processes for making the polydiorganosiloxane diamines resulted in increasing levels of monofunctional impurities with increasing molecular weight, it was not possible to achieve elastomers having satisfactory mechanical properties for most elastomer or adhesive applications. More recently, processes have been developed that produce low levels of impurities over a wide range of polydiorganosiloxane diamine molecular weights. With these processes polydiorganosiloxane polyurea segmented copolymers have been obtained that have good mechanical properties through the use of chain extenders to increase the non-silicone content. However, these systems, with or without chain extender, do not flow at room temperature.
Continuous melt polymerization processes have been used to produce polyurethane elastomers and acrylate pressure-sensitive adhesives. Polyetherimides, which can contain polydiorganosiloxane segments, have also been produced in a continuous melt polymerization process. Recently polyurethane resins have been described that use polydiorganosiloxane urea segments to prevent blocking of films formed from the resin. However, levels of reactive polydiorganosiloxane in the compositions were small, for example, less than 15 weight percent, and incomplete incorporation of the polydiorganosiloxane into the backbone was not detrimental since easy release was the intent. Unincorporated polydiorganosiloxane oil can, however, act as a plasticizing agent in elastomers to reduce tensile strength or detackify and reduce shear properties of pressure-sensitive adhesives. This unincorporated oil can also bloom to the surface of an elastomer or adhesive and contaminate other surfaces with which it is in contact.
Briefly, in one aspect of the present invention, polydiorganosiloxane oligourea segmented copolymers are provided wherein such copolymers comprise soft polydiorganosiloxane diamine units, hard polyisocyanate residue units, wherein the polyisocyanate residue is the polyisocyanate minus the xe2x80x94NCO groups, optionally, soft and/or hard organic polyamine units, wherein residues of the isocyanates amine units are connected by urea linkages, and terminal groups, wherein the terminals groups are non-functional endcapping groups or functional endcapping groups.
The present invention further provides polydiorganosiloxane oligourea segmented copolymer compositions comprising the reaction product of
(a) at least one polyisocyanate;
(b) an endcapping agent having a terminal selected from polydiorganosiloxane monoamines and non-siloxane containing endcapping agents having a terminal portion reactive with an amine or isocyanate and a terminal portion that is non-functional or that can react under moisture-cure or free-radical conditions,
with the provisos (1) that if no polydiorganosiloxane monoamine is present, then at least one polyamine is present, wherein polyamine comprises at least one polydiorganosiloxane diamine or a mixture of at least one polydiorganosiloxane diamine and at least one organic polyamine, (2) if only polyisocyanate and polyamine are present, the molar ratio of isocyanate to amine is  less than 0.9:1 or  greater than 1.1:1, and (3) when polydiorganosiloxane monoamine and diamine are present, the ratio of total isocyanate available in the polyisocyanate to the total amine available in the monoamine and diamine less any amine end groups in the copolymer is about 1:1.
The polydiorganosiloxane oligourea segmented copolymer compositions of the present invention can be represented by Formula I. Anyone knowledgeable in the art would know that the oligomerization process leads to randomization of the polydiorganosiloxane diamine and organic polyamines along the back one. This could lead to the organic polyamine reacting with the endcapper. 
wherein
each Z is a polyvalent radical selected from arylene radicals and aralkylene radicals preferably having from about 6 to 20 carbon atoms, alkylene and cycloalkylene radicals preferably having from about 6 to 20 carbon atoms, preferably Z is 2,6-tolylene, 4,4xe2x80x2-melthylenediphenylene, 3,3xe2x80x2-dimethoxy-4,4xe2x80x2-biphenylene, tetramethyl-m-xylylene, 4,4xe2x80x2-methylenedicyclohexylene, 3,5,5-trimethyl-3-methylenecyclohexylene, 2,2,4-trimethylhexylene, 1,6-hexamethylene, 1,4-cyclohexylene, and mixtures thereof;
each R is a moiety independently selected from alkyl moieties preferably having about 1 to 12 carbon atoms and may be substituted with, for example, trifluoroalkyl or vinyl groups, a vinyl radical or higher alkenyl radical preferably represented by the formula xe2x80x94R2(CH2)aCHxe2x95x90CH2 wherein R2 is xe2x80x94(CH2)bxe2x80x94 or xe2x80x94(CH2)cCHxe2x95x90CHxe2x80x94 and a is 1, 2 or 3, b is 0, 3 or 6; and c is 3, 4 or 5; a cycloalkyl moiety having about 6 to 12 carbon atoms and may be substituted with alkyl, fluoroalkyl, and vinyl groups, or an aryl moiety preferably having about 6 to 20 carbon atoms and that may be substituted with, for example, alkyl, cycloalkyl, fluoroalkyl and vinyl groups or R is a perfluoroalkyl group as described in U.S. Pat. No. 5,028,679, wherein such description is incorporated herein by reference, a fluorine-containing group as described in U.S. Pat. No. 5,236,997, wherein such description is incorporated herein by reference or a perfluoroether-containing group, as described in U.S. Pat. Nos. 4,900,474 and 5,118,775, wherein such descriptions are incorporated herein by reference, preferably at least 50% of the R moieties are methyl radicals with the balance being monovalent alkyl or substituted alkyl radicals having 1 to 12 carbon atoms, vinylene radicals, phenyl radicals, or substituted phenyl radicals;
each Y is a polyvalent moiety independently selected from an alkylene radical preferably having 1 to 10 carbon atoms, aralkylene radical and arylene radical, preferably having 6 to 20 carbon atoms;
each D is independently selected from hydrogen, alkyl radicals preferably having 1 to 10 carbon atoms, phenyl, and a radical that completes a ring structure including B or Y to form a heterocycle, preferably having about 6 to 20 carbon atoms;
each A is independently xe2x80x94Bxe2x80x94, or xe2x80x94YSi(R)2(OSi(R)2)pYxe2x80x94 or mixtures thereof;
B is a polyvalent radical selected from the group consisting of alkylene, aralkylene, cycloalkylene, phenylene, polyalkylene oxide, such as, polyethylene oxide, polypropylene oxide, polytetramethylene oxide, and copolymers thereof, and mixtures thereof;
m is a number that is 0 to about 8;
b, e, d and n are 0 or 1, with the provisos that, b+d=1 and e+n=1;
p is about 10 or larger, preferably about 15 to 2000, more preferably about 30 to 1500;
q is about 10 or larger, preferably about 15 to 2000, more preferably about 30 to 1500; and
t is a number which is 0 to about 8;
s is 0 or 1; and
each X is independently:
(a) a moiety represented by 
wherein D is defined as above;
(b) a moiety represented by 
where each of D, and Z are defined as above,
(c) a monovalent moiety that is not reactive under moisture curing or free radical curing conditions and that can be the same or different and that are alkyl moieties preferably having about 1 to 20 carbon atoms and that can be substituted with, for example, trifluoroalkyl groups, or aryl moieties preferably having about 6 to 20 carbon atoms and that may be substituted with, for example alkyl, aryl, and substituted aryl groups and a particularly useful embodiment when X is C, is when t=0 and m=0;
(d) a moiety represented by 
where each of Z, and D are defined as above,
K is independently (i) a moiety that is not reactive under moisture curing or free radical curing conditions and that can be the same or different selected from the group consisting of alkyl, substituted alkyl, aryl, and substituted aryl; (ii) a free radically curable end group such as, for example acrylate, methacrylate, acrylamido, methacrylamido and vinyl groups; (iii) a moisture curable group such as, for example, alkoxysilane and oxime silane groups, and
(e) a moiety represented by 
wherein D, Y and K are defined as above.
In the use of polyisocyanates (Z is a radical having a functionality greater than 2) and polyamines (B is a radical having a functionality greater than 2), the structure of Formula I will be modified to reflect branching at the polymer backbone.
The average degree of oligomerization refers to the size of the resultant oligomer molecule and is determined from the number average of the residue of amine-containing reactant molecules in the oligomer. There are two ways of obtaining the desired degree of oligomerization: (1) control the isocyanate to amine ratio to obtain either isocyanate or amine endcapped oligomer (X=a or b), and (2) judiciously select the amount of monoamine or monoisocyanate endcapper with stoichiometric amounts of isocyanate and amine (X=c, d, or e). The following table displays the mol ratios of the various molecules necessary for building a molecule with the desired endcapper X. For the use of polyamines and polyisocyanates, the ratios may be adjusted accordingly.
The polydiorganosiloxane oligourea segmented copolymers of the present invention can be prepared to exhibit desired controlled flow properties in the uncured state, being liquid or semi-solid at ambient temperatures. The controlled flow properties of the copolymer can be optimized by appropriate selection of the polyisocyanate, the molecular weight of the polydiorganosiloxane amine, the average degree of oligomerization, the organic polyamine selected, and the nature of Z. Generally, the green strength of the resultant polydiorganosiloxane polyurea segmented oligomer increases with decreasing polydiorganosiloxane amine molecular weight. The compositions of the present invention have an average degree of oligomerization of between 2 and 12.
The polydiorganosiloxane oligourea segmented copolymers of the present invention have diverse utility. The copolymers possess the conventional excellent physical properties associated with polysiloxanes of low glass transition temperature, high thermal and oxidative stabilities, UV resistance, low surface energy and hydrophobicity, good electrical properties and high permeability to many gases.
When the polydiorganosiloxane oligourea segmented copolymers are terminated with non-functional end groups, the resulting copolymers possess the thermally reversible properties of a gel, semisolid, or solid at room temperature and of a fluid at elevated temperatures. Selected polydiorganosiloxane oligourea segmented copolymers of the present invention have a surprisingly low melt flow viscosity and abrupt solidification at a temperature below the melt flow conditions. Additionally, these selected copolymers exhibit ease of reprocessing without additional stabilizers that make them suitable as thermally reversible encapsulants and potting compounds or as caulking compounds where sharp or reversible liquid/solid transitions are desired, for example, such as in assembly line operations.
Advantageously, the selection of the terminal group used to prepare the copolymers of the present invention can provide a variety of materials having various properties. The terminal groups of the copolymer can either be non-functional or functional. If the terminal group is a functional end-capping group, the resultant copolymers have a latent reactivity, such that these functional end-capped copolymers can serve as prepolymer units, can be crosslinked, can be cured, and the like.
When the polydiorganosiloxane oligourea segmented copolymers of the present invention are terminated with reactive amine end groups, they can be further reacted with multifunctional isocyanates, multifunctional acrylates, multifunctional anhydrides, or mixtures thereof to obtain various crosslinked branched, or chain-extended materials.
When the polydiorganosiloxane oligourea segmented copolymers of the present invention are terminated wvitlh reactive isocyanate end groups, they can be further reacted with water, multifunctional amines, multifunctional alcohols, multifunctional mercaptans, or mixtures thereof to obtain various crosslinked branched, or chain-extended materials.
Additionally, when the polydiorganosiloxane oligourea segmented copolymers of the invention are terminated with a chemically curable end group, the resulting green strength, that is, strength prior to curing, is generally greater than that for chemically crosslinkable silicone compositions known in the art.
The polydiorganosiloxane oligourea segmented copolymers of the present invention having free radically curable end groups can be solution coated or hot melt coated easily without placirg adverse stresses into the coating and can be formed into irregular shapes that will hold their shape until they are thermally or radiation cured. Such a feature makes them useful, for example, in applications such as gaskets, sealants, and replicated surfaces and coatings on easily deformable substrates.
The polydiorganosiloxane oligourea segmented copolymers of the present invention having moisture curable end groups can be solution coated or hot melt coated in a manner similar to the free radically cured forms, or applied to a variety of irregular substrates in situations that do not allow subsequent thermal or radiation curing treatments or in which free radical reactions are inhibited by the presence of oxygen. Such characteristics make them useful, for example, in applications in the building construction industry, such as caulking and sealants, and in areas where oxygen inhibited radiation or thermal treatments are not preferred.
The polydiorganosiloxane oligourea segmented copolymers of the present invention with both free radically curable end groups and moisture curable end groups are useful, for example, in situations where partial cure by one mechanism is desirable followed by complete cure by another method. Areas where this feature is useful include situations where a subsequent manufacturing operation is desired and superior green strength is beneficial, such as in assembly line operations.
The present invention further provides a solvent process and a solventless process for producing the polydiorganosiloxane oligourea segmented copolymers of the present invention.
The solvent process comprises the steps of
providing reactants, wherein the reactants comprise (a) a polyisocyanate; (b) an endcapping agent selected from polydiorganosiloxane monoamines and non-siloxane containing endcapping agents having a terminal portion reactive with an amine or isocyanate and a terminal portion that is non-functional or that can react under moisture-cure or free-radical conditions; with the provisos (1) that if no polydiorganosiloxane monoamine is present, then at least one polyamine is present, wherein polyamine comprises at least one polydiorganosiloxane diamine or mixtures of at least one polydiorganosilxane diamine and at least one organic polyamine, (2) if only polyisocyanate and polyamine are present, the molar ratio of isocyanate to amine is  less than 0.9:1 or  greater than 1.1:1, and (3) when polydiorganosiloxane monoamine and diamine are present, the ratio of total isocyanate available in the polyisocyanate to the total amine available in the monoamine and diamine less any amine end groups in the copolymer is about 1:1; and (c) solvent to a reactor;
mixing the reactants in the reactor;
allowing the reactants to react to form a polydiorganosiloxane oligourea segmented copolymer with an average degree of oligomerization of 2 to 12; and
conveying the oligomer from the reactor.
The solventless process comprises the steps of:
continuously providing (a) a polyisocyanate; (b) an endcapping agent selected from polydiorganosiloxane monoamines and non-siloxane containing endcapping agents having a terminal portion reactive with an amine or isocyanate and a terminal portion that is non-functional or that can react under moisture-cure or free-radical conditions;
with the provisos (1) that if no polydiorganosiloxane monoamine is present, then at least one polyamine is present, wherein polyamine comprises at least one polydiorganosiloxane diamine or a mixture of at least one polydiorganosiloxane diamine and at least one organic polyamine, (2) if only polyisocyanate and polyamine are present, the molar ratio of isocyanate to amine is  less than 0.9:1 or  greater than 1.1:1, and (3) when polydiorganosiloxane monoamine and diamine are present, the ratio of total isocyanate available in the polyisocyanate to the total amine available in the monoamine and diamine less any amine end groups in the copolymer is about 1:1, to a reactor under substantially solventless conditions;
mixing the reactants in the reactor under the substantially solventless conditions;
allowing the reactants to react to form a polydiorganosiloxane oligourea segmented copolymer with a average degree of oligomerization of 2 to 12; and
conveying the oligomer from the reactor.
In the solventless process, generally, no solvent is needed to carry out the reaction, making the process more environmentally friendly than the solvent process for making polydiorganosiloxane oligourea segmented copolymers. Small amounts of solvent may be present, if necessary, to control the flow of solid polyisocyanates, high viscosity polyisocyanates, low amounts of polyisocyanates, or for controlled addition of adjuvants such as tackifying resins, pigments, crosslinking agents, plasticizers, fillers, and stabilizing agents, or to reduce their viscosity. An additional benefit of the continuous, solventless process of the present invention is the ability to extrude the polydiorganosiloxane polyurea segmented oligomer into thick constructions, into patterned shapes or onto irregularly-shaped surfaces directly after polymerization.
Different polyisocyanates in the reaction will modify the properties of the polydiorganosiloxane oligourea segmented copolymer. For example, if a polycarbodiimide-modified diphenylmethane diisocyanate, such as ISONATE(trademark) 143L, available from Dow Chemical Co., is used, the resulting polydiorganosiloxane oligourea segmented copolymer has superior solvent resistance when compared with other polyisocyanates. If tetramethyl-m-xylylene diisocyanate is used, the resulting segmented copolymer may be a semisolid to solid gel that has a very low melt viscosity that makes it particularly useful in potting and sealant applications where thermal reversibility is advantageous.
Any diisocyanate that can be represented by the formula
OCNxe2x80x94Zxe2x80x94NCO
wherein Z is as defined above, can be used in the present invention. Examples of such diisocyanates include, but are not limited to, aromatic diisocyanates, such as 2,6-toluene diisocyanate, 2,5-toluene diisocyanate, 2,4-toluene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, methylene bis(o-chlorophenyl diisocyanate), methylenediphenylene-4,4xe2x80x2-diisocyanate, polycarbodiimide-modified methylenediphenylene diisocyanate, (4,4xe2x80x2-diisocyanato-3,3xe2x80x2, 5, 5xe2x80x2-tetraethyl) biphenylmethane, 4,4xe2x80x2-diisocyanato-3,3xe2x80x2-dimethoxybiphenyl (o-dianisidine diisocyanate), 5-chloro-2,4-toluene diisocyanate, 1-chloromethyl-2,4-diisocyanato benzene, aromatic-aliphatic diisocyanates such as m-xylylene diisocyanate, tetramethyl-m-xylylene diisocyanate, aliphatic diisocyanates, such as 1,4-diisocyanatobutane, 1,6-diisocyanatohexane, 2,2,4-trimethylhexyl diisocyanate, 1,12-diisocyanatododecane, 2-methyl-1,5-diisocyanatopentane, and cycloaliphatic diisocyanates such as methylene-dicyclohexylene-4,4xe2x80x2-diisocyanate, and 3-isocyanatomethyl-3,5,5-trimethyl-cyclohexyl isocyanate and mixtures thereof.
Preferred diisocyanates include 2,6-toluene diisocyanate, methylenediphenylene-4,4xe2x80x2-diisocyanate, polycarbodiimide-modified methylenediphenyl diisocyanate, o-dianisidine diisocyanate, tetramethyl-m-xylylene diisocyanate, methylenedicyclohexylene-4,4xe2x80x2-diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (isophorone diisocyanate), 2,2,4-trimethylhexyl diisocyanate, 1,6-diisocyanatohexane, and cyclohexylene-1,4-diisocyanate. Particularly preferred is tetramethyl-m-xylylene diisocyanate and mixtures thereof.
Any triisocyanate that can react with a monoamine and polyamine can be used in the present invention. Examples of such triisocyanates include, but are not limited to, polyfunctional isocyanates, such as those produced from biurets, isocyanurates, adducts, and the like, may be used. Some commercially available polyisocyanates include portions of the DESMODUR(trademark) and MONDUR(trademark) series from Bayer and the PAPI series of Dow Plastics.
Preferred triisocyanates include DESMODUR(trademark) N-3300 and MONDUR(trademark) 489.
Terminal Groups
Polydiorganosiloxane monoamines useful in the present invention as end capping agents can be represented by the formula 
where D, R, X(c), Y and q are as described above, and include those having number average molecular weights in the range of about 700 to 150,000. Preferred are polydiorganosiloxane monoamines prepared as deescribed in U.S. Pat. No. 5,091,483, wherein such description is incorporated herein by reference. The polydiorganosiloxane monoamines can be prepared, for example, from the reaction of cyclic organotrisiloxanes with alkyl lithium reagents in tetrahydrofuran to yield lithium polydiorganosiloxanolates that are subsequently reacted with aminoalkylfluorosilanes as terminating agents to provide the polydiorganosiloxane monoamine product.
Examples of siloxane monoamines useful in the present invention include polydimethylsiloxane monoamine, polydiphenylsiloxane monoamine, polytrifluoropropylmethylsiloxane monoamine, polyphenylmethylsiloxane monoamine, polydiethylsiloxane monoamine, polydivinylsiloxane monoamine, polyvinylmethylsiloxane monoamine, and copolymers thereof and mixtures thereof.
Suitable endcapping agents for polydiorganosiloxane oligourea segmented copolymers that would be terminated with amine groups, were no endcapping agent present, and that provide terminal groups that are not reactive under moisture curing or free radical curing conditions include but are not limited to monoisocyanates such as alkyl isocyanates, such as benzyl isocyanate, cyclohexyl isocyanate, n-dodecyl isocyanate, n-octadecyl isocyanate, octyl isocyanate, 2-phenylethyl isocyanate, trimethylsilyl isocyanate, undecyl isocyanate; and aryl isocyanates, such as 4-bromophenyl isocyanate, 2-chlorophenyl isocyanate, 2,4-dimethylphenyl isocyanate, 1-naphthyl isocyanate, phenyl isocyanate, 4-tolyl isocyanate, 4-trifluoromethylphenyl isocyanate, 2,4,6-trimethylphenyl isocyanate.
Suitable endcapping agents for polydiorganosiloxane oligourea segmented copolymers that would be terminated with isocyanate groups, were no endcapping agent present, and provide terminal groups that are not reactive under moisture curing or free radical curing conditions include but are not limited to organic monoamines such as propylamine, cyclohexylamine, aniline, benzylamine, octadecylamine, phenylethylamine, and polyoxyalkylene monoamine, such as those that can be obtained from Huntsman, Corp. under the tradename of Jeffamine, polyethylene oxide, polypropylene oxide, copolymers thereof and mixtures thereof.
Suitable endcapping agents for polydiorganosiloxane oligourea segmented copolymers that would be terminated with amine groups, were no endcapping agent present, and that provide terminal groups that are reactive under free radical curing conditions, include but are not limited to isocyanatoethyl methacrylate; alkenyl azlactones such as vinyl dimethyl azlactone and isopropenyl dimethyl azlactone, m-isopropenyl-xcex1,xcex1-dimethyl benzyl isocyanate, and acryloyl ethyl carbonic anhydride. Some endcapping agents that can react with amine groups, e.g., isocyanatoethyl methacrylate, are commercially available, and others can be prepared using known methods. Alkenyl azlactones and their preparations are described, for example, in U.S. Pat. No. 4,777,276, wherein such description is incorporated herein by reference. Acryloyl ethyl carbonic anhydride can be prepared from ethyl chloroformate and acrylic acid as described in R. Hatada et al., Bull. Chem. Soc, Japan, 41 (10), 2521 (1968). Preferred endcapping agents for polydiorganosiloxane oligourea segmented copolymers that would be amine terminated if no endcapping agent were present include, for example, isocyanatoethyl methacrylate, vinyl dimethyl azlactone, and acryloyl ethyl carbonic anhydride.
Suitable endcapping agents for polydiorganosiloxane oligourea segmented copolymers that would be amine terminated, if no endcapping agent were present, to provide terminal groups that are reactive under nmoisture curing conditions include but are not limited to isocyanatopropyl trimethoxysilane, isocyanatopropyl triethoxysilane, isocyanatopropyl dimethoxy (methylethylketoximino)silane, isocyanatopropyl diethoxy (methylethylketoximino)silane, isocyanatopropyl monomethoxy di(methylethylketoximino)silane, isocyanatopropyl monoethoxy di(methylethylketoximino)silane, and isocyanatopropyl tri(methylethylketoximino)silane. Polyisocyanates that serve to form the copolymer, may also serve as the moisture curable terminal portion of the copolymer when the number of isocyanate groups provided by the polyisocyanates exceed the amine groups provided by the polyamines. Polymers prepared with such end-capping agents can be further reacted to provide higher molecular weight polymers or copolymers.
Suitable endcappiug agents for polydiorganosiloxane oligourea segmented copolymers that would be isocyanate terminated if no endcapping agent were present to provide terminal groups that are reactive under moisture curing conditions include but are not limited by aminopropyl trimethoxysilane, aminopropyl triethoxysilane, aminopropyl methyldimethoxysilane, aminopropyl methyldiethoxysilane, aminopropyl dimethoxy(methylethylketoximino)silane, aminopropyl diethoxy(methylethylketoximino)silane, aminopropyl monomethoxydi(methylethylketoximino)silane, aminopropyl monoethoxydi(methylethylketoximino)silane, and aminopropyl tri(methylethylketoximino)silane mixtures thereof and partial hydrolyzates thereof. Preferred endcapping agents, for isocyanate-terminated polydiorganosiloxane polyurea segmented oligomers, if no end-capping agents were present to provide terminal groups that are reactive under various conditions, include those selected from the group consisting of aminopropyl trimethoxysilane, aminopropyl triethoxysilane and aminopropyl methyldiethoxysilane.
Polydiorganosiloxane diamines useful in the present invention can be represented by the formula 
R, Y, D and p are defined as above and includes those having number average molecular weights in the range of about 700 to 150,000.
Preferred diamines are substantially pure polydiorganosiloxane diamines prepared as described in U.S. Pat. No. 5,214,119, wherein such description is incorporated herein by reference. High purity polydiorganosiloxane diamines are prepared from the reaction of cyclic organosiloxanes and bis(aminoalkyl)disiloxanes utilizing an anhydrous amino alkyl functional silanolate catalyst such as tetramethylammonium 3-aminopropyldimethylsilanolate, preferably in an amount less than 0.15 weight percent based on the total weight of the cyclic organosiloxanes with the reaction run in two stages.
Particularly preferred are polydiorganosiloxane diamines prepared using cesium and rubidium catalysts.
Preparation includes combining under reaction conditions
(1) an amine functional end-capping agent represented by the formula: 
xe2x80x83wherein each R, Y, D andp are defined as above and x is an integer of about 0 to 150;
(2) sufficient cyclic siloxane to obtain a polydiorganosiloxane diamine having a molecular weight greater than the molecular weight of the end-capping agent and
(3) a catalytically effective amount of cesium hydroxide, rubidium hydroxide, cesium silanolate, rubidium silanolate, cesium polysiloxanolate, rubidium polysiloxanolate, and mixtures thereof.
The reaction is continued until substantially all of the amine functional end-capping agent is consumed. Then the reaction is terminated by adding a volatile organic acid to form a mixture of a polydiorganosiloxane diamine usually having greater than about 0.01 weight percent silanol impurities and one or more of the following, a cesium salt of the organic acid, a rubidium salt of the organic acid, or both such that there is a small molar excess of organic acid in relation to catalyst. Then, the silanol groups of the reaction product are condensed under reaction conditions to form polydiorganosiloxane diamine having less than or equal to about 0.01 weight percent silanol impurities while the unreacted cyclic siloxane is stripped, and, optionally, the salt is removed by subsequent filtration.
Examples of polydiorganosiloxane diamines useful in the present invention include polydimethylsiloxane diamine, polydiphenylsiloxane diamine, polytrifluoropropylmethylsiloxane diamine, polyphenylmethylsiloxane diamine, polydiethylsiloxane diamine, polydivinylsiloxane diamine, polyvinylmethylsiloxane diamine, poly(5-hexenyl)methylsiloxane diamine, mixtures and copolymers thereof.
Examples of organic polyamines useful in the present invention include but are not limited to polyoxyalkylene diamine, such as D-230, D-400, D-2000, D-4000, DU-700, ED-2001 and EDR-148, all available from Huntsman, polyoxyalkylene triamine, such as T-3000 and T-5000 available from Huntsman, polyalkylenes, such as Dytek A and Dytek EP, available from DuPont.
The above polyamines, polyisocyanates, and endcapping agents are used in the appropriate stoichiometric ratios to obtain curable polydiorganosiloxane oligourea segmented copolymers with the desired average degree of polymerization.
Silane agents may be used to crosslink the moisture curable polysiloxane oligourea segmented copolymers of the present invention. Suitable silane agents generally have the formula Rxe2x80x3nSiW4-n where Rxe2x80x3 is a monovalent hydrocarbon group, (for example, an alkyl, alkylenyl, aryl, or alkaryl group), n is 0, 1 or 2, and W is a monovalent hydrolyzable group such as a dialkylketoximino group, (for example, methylethylketoximino, dimethylketoximino, or diethylketoximino), alkoxy group (for example, methoxy, ethoxy, or butoxy), alkenoxy group (for example, isopropenoxy), acyloxy group (for example, acetoxy), alkamido group (for example, methylacetamido or ethylacetamido), or acylamido group (for example, phthalimidoamido). Silane crosslinking agents falling within this category are commercially available, for example, from Silar Laboratories, Scotia, N.Y. Particularly preferred silane crosslinking agents are dialkylketoximinosilanes because they exhibit good shelf-stability and do not form deleterious by-products upon cure. Examples include methyltri(methylethylketoximino) silane and vinyltri(methylethylketoximino) silane, both of which are commercially available from Allied-Signal, Inc. Morristown, N.J., and alkoxysilanes available from OSi Chemicals, Lisle, Ill.
The free radically curable polydiorganosiloxane oligourea segmented copolymer compositions of the invention can, depending upon their viscosity, be coated, extruded, or poured, and rapidly, completely, and reliably radiation cured to elastomers (even at high molecular weight) by exposure to electron beam, visible or ultraviolet radiation. Curing should be carried out in as oxygen-free an environment as possible, e.g., in an inert atmosphere such as nitrogen gas or by utilizing a barrier of radiation-transparent material having low oxygen permeability. Curing can also be carried out under an inerting fluid such as water. When visible or ultraviolet radiation is used for curing, the silicone compositions may also contain at least one photoinitiator. Suitable photoinitiators include benzoin ethers, benzophenone and derivatives thereof, acetophenone derivatives, camphorquinone, and the like. Photoinitiator is generally used at a concentration of from about 0.1% to about 5% by weight of the total polymerizable composition, and, if curing is carried out under an inerting fluid, the fluid is preferably saturated with the photoinitiator or photoinitiators being utilized in order to avoid the leaching of initiator from the silicone composition. The rapid cure observed for these materials allows for the use of very low levels of photoinitiator relative to what is known in the art, hence uniform cure of thick sections can be achieved due to deeper penetration of radiation. If desired, the silicone compositions of this invention can also be cured thermally, requiring the use of thermal initiator such as peroxides, azo compounds, or persulfates generally at a concentration of from about 1% to about 5% by weight of the total polymerizable composition. Preferably any thermal or photo-initiator used is soluble in the silicone compositions themselves, requiring little or no use of a solvent to dissolve the initiator.
Examples of suitable curing catalysts for moisture curable polydiorganosiloxane oligourea segmented copolymers include alkyl tin derivatives (e.g., dibutyltindilaurate, dibutyltindiacetate, and dibutyltindioctoate commercially available as xe2x80x9cT-series Catalystsxe2x80x9d from Air Products and Chemicals, Inc. of Allentown, Pa.), and alkyl titanates (e.g., tetraisobutylorthotitanate, titanium acetylacetonate, and acetoacetic ester titanate commercially available from DuPont under the designation xe2x80x9cTYZORxe2x80x9d). In general, however, it is preferred to select silane crosslinking agents that do not require the use of curing catalysts to avoid reducing shelf-life and adversely affecting the physical properties of the composition.
Other catalysts useful for moisture curable polydiorganosiloxane oligourea segmented copolymers include acids, anhydrides, and lower alkyl ammonium salts thereof that include but are not limited to those selected from the group consisting of trichloroacetic acid, cyanoacetic acid, malonic acid, nitroacetic acid, dichloroacetic acid, difluoroacetic acid, trichloroacetic anhydride, dichloroacetic anhydride, difluoroacetic anhydride, triethylammonium trichloroacetate, trimethylammonium trichloroacetate, and mixtures thereof.
Also useful for curing compositions of this invention are the well known two component room temperature free radical curatives consisting of a polymerization catalyst and an accelerator. Common polymerization catalysts useful in this two component curative include organic peroxides and hydroperoxides such as dibenzoyl peroxide, t-butyl hydroperoxide, and cumene hydroperoxide, that are not active at room temperature in the absence of an accelerator. The accelerator component of the curative consists of the condensation reaction product of a primary or secondary amine and an aldehyde. Common accelerators of this type are butyraldehyde-aniline and butyraldehyde-butylamine condensation products sold by E. I. duPont de Nemours and Co. as Accelerator 808(trademark) and Accelerator 833(trademark). This catalyst system may be employed to prepare a two-part free radically curable organosiloxane oligourea segmented copolymer where the curable copolymrer is divided into two parts and to one part is added the polymerization catalyst and to the other part is added the accelerator. Upon mixing this two component system cures at room temperature. Alternatively, the polymerization catalyst can be incorporated in the free radically curable organosiloxane oligourea segmented copolymer and the accelerator can be applied to a substrate such that when the free radically curable organosiloxane oligourea segmented copolymer containing polymerization catalyst contacts the xe2x80x9cprimedxe2x80x9d substrate surface, cure proceeds immediately at room temperature. Those of ordinary skill in the art are familiar with such cure systems and could readily adapt them to various product constructions.
Fillers, tackifying resins, plasticizers, and other property modifiers may be incorporated in the polydiorganosiloxane polyurea segmented oligomers of the present invention. Generally, such modifiers are used in amounts ranging up to about 80 weight percent. Additives such as dyes, pigments, stabilizers, antioxidants, compatibilizers, and the like can also be incorporated into the polydiorganosiloxane polyurea segmented copolymers of the invention. Generally, such additives are used in amounts ranging up to about 20 weight percent.
Specific characteristics of the polydiorganosiloxane oligourea segmented copolymers of the invention can be influenced by a number of factors including 1) the nature of the xe2x80x9cKxe2x80x9d group, when present, 2) the nature of the diisocyanate group used, 3) the molecular weight of the polydiorganosiloxane monoamine and/or polydiorganosiloxane diamine used, 4) the presence of an organic polyamine, 5) the average degree of oligomerization, and 6) whether significant excesses of polyisocyanate or polyamine exist. The nature of the xe2x80x9cKxe2x80x9d group largely determines whether or not the copolymer is curable, by what mechanism, and under what conditions.
The nature of the isocyanate residue in the polydiorganosiloxane oligourea segmented copolymer influences stiffness and flow properties, and also affects the properties of the cured copolymers. Isocyanate residues resulting from diisocyanates that form crystallizable ureas, such as tetramethyl-m-xylylene diisocyanate, 1,12-dodecane diisocyanate, dianisidine diisocyanate, provide copolymers that are stiffer than those prepared from methylenedicyclohexylene-4,4xe2x80x2-diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, and m-xylylene diisocyanate.
The molecular weight of the polydiorganosiloxane monoamine or diamine, if present, affects the elasticity of the polydiorganosiloxane oligourea segmented copolymers. Lower molecular weight diamines result in polydiorganosiloxane oligourea segmented copolymers having higher modulus and higher tensile strength when cured. Higher molecular weight diamines provide copolymers having lower modulus but higher strain at break. The average degree of oligomerization affects the rheological properties of the uncured oligomer and may affect the mechanical properties of the cured oligomer. The average degree of oligomerization affects the rheological properties with increasing degrees of oligomerization. Excess polyisocyanate or polyamine may affect the reactivity of the oligomer with other reactive moieties.
The materials of the invention can be made by a solvent process and by a solventless process. In both processes of the present invention, the reactants and optional nonreactive additives are mixed in a reactor and allowed to react to form the polydiorganosiloxane polyurea segmented oligomers having an average degree of oligomerization of from 2 to 12 and that can then be removed from the reaction vessel. When isocyanate functional endcapping agents are utilized, such agents can, for example, be mixed with the other isocyanate reactants before they are introduced into the reactor. Similarly, amine-functional endcapping agents for example, may be mixed with polydiorganosiloxane diamine reactants before they are introduced into the reactor.
In the following discussion of the two processes, an isocyanate functional endcapping agent, different from the diisocyanate reactant, is utilized.
For the solvent based process, the reaction solvents and starting materials are usually purified and dried and the reaction is carried out under an inert atmosphere such as dry nitrogen or argon.
The preferred reaction solvents are those that are unreactive with the isocyanate functional reactants, the amine functional reactants and the endcapping agents and that maintain the reactants and product completely in solution throughout the polymerization reaction. Generally, chlorinated solvents, ethers, and alcohols are preferred with aliphatic diisocyanates, with methylene chloride, tetrahydrofuran, and isopropyl alcohol being particularly preferred. When reactants include aromatic diisocyanates such as methylenediphenylene-4,4xe2x80x2-diisocyanate (MDI), a mixture of tetrahydrofuran with 10% to 25% by weight of dipolar aprotic solvent such as dimethylformamide is preferred.
In the substantially solventless process, the flexibility of the process leads to interesting materials. One skilled in the art can expect the optimum material for a particular application to be a function of the architecture and ratios of reactants, mixing speed, temperature, reactor throughput, reactor configuration and size, residence time, residence time distribution, optionai initiator architecture, and whether any fillers, additives, or property modifiers are added.
Any reactor that can provide intimate mixing of the polyisocyanates and polyamines is suitable for use in substantially solventless process of the present invention. The reaction may be carried out as a batch process using, for example, a flask equipped with a mechanical stirrer, provided the product of the reaction has a sufficiently low viscosity at the processing temperature to permit mixing, or as a continuous process using, for example a single screw or twin screw extruder. Preferably, the reactor is a wiped surface counter-rotating or co-rotating twin screw extruder.
Temperatures in the reactor should be sufficient to permit reaction between the polyisocyanate and the polyamine to occur. The temperature should be sufficient to permit conveying of the materials through the reactor, and any subsequent processing equipment such as, for example, feedblocks and dies. For conveying the reacted material, the temperature should preferably be in the range of about 20 to 250xc2x0 C., more preferably in the range of about 20 to 200xc2x0 C. Residence time in the reactor typically varies from about 5 seconds to 8 minutes, more typically from about 15 seconds to 3 minutes.
The residence time depends on several parameters, including, for example, the length to diameter ratio of the reactor, mixing rates, overall flowrates, reactants, and the need to blend in additional materials. For materials involving reaction with minimal or no blending of a nonreactive component, the reaction can easily take place in as little as 5:1 length to diameter units of a twin screw extruder.
When a wiped surface reactor is used, it preferably has relatively close clearances between the screw flight lands and the barrel, with this value typically lying between 0.1 to about 2 mm. The screws utilized are preferably fully or partially intermeshing or fully or partially wiped in the zones where a substantial portion of the reaction takes place.
Because of the rapid reaction that occurs between the polyisocyanates and polyamines, the materials are preferably fed into an extuder at unvarying rates, particularly when using higher molecular weight polydiorganosiloxane amines, i.e., with number average molecular weights of about 50,000 and higher. Such feeding generally reduces undesirable variability of the final product.
One method of ensuring the continuous feeding of very low flow polyisocyanate quantities in an extruder is to first mix the endcapping agent with the polyisocyanate and then to allow the polyisocyanate and isocyanate-functional endcapping agent feed line to touch or very nearly touch the passing threads of the screws. Another method would be to utilize a continuous spray injection device that produces a continuous stream of fine droplets of the polyisocyanate and isocyanate-functional endcapping agent into the reactor.
However, the various reactants and additives can be added in any order provided the addition of an additive does not interfere with the reaction of the reactants. An additive that is particularly reactive with a polyisocyanate reactant typically would not be added until after the reaction of the polyisocyanate with a polyamine reactant. Further, the reactants can be added simultaneously or sequentially into the reactor and in any sequential order, for example, the polyisocyanate stream can be the first component added into the reactor in a manner such as mentioned above. Polyamine can then be added downstream in the reactor. Alternately, the polyisocyanate stream can also be added after the polyamine has been introduced into the reactor.
The process of the present invention has several advantages over conventional solution polymerization processes for making polydiorganosiloxane polyurea segmented copolymers such as (1) the ability to vary the polyisocyanate-to-polyamine ratio to obtain materials with properties superior to solution polymerized materials, (2) the capabiility of polymerizing high molecular weight compositions that cannot be easily produced using solution polymerization, (3) the ability to directly produce shaped articles with reduced heat histories, (4) the ability to directly blend in fillers, tackifying resins, plasticizers, and other property modifiers, and (5) the elimination of solvent.
The flexibility of altering the polyisocyanate-to-polyamine ratio in the continuous process is a distinct advantage. This ratio can be varied above and below the theoretical value of 1:1 quite easily.
The polyisocyanate and isocyanate-functional endcapping agent stream can be the first component added into the reactor in a manner such as mentioned above. The polydiorganosiloxane amine can then be added downstream in the reactor. Alternately, the diisocyanate and isocyanate functional endcapping agent stream can also be added after the polydiorganosiloxane amine stream has been introduced into the reactor.
In formulating the polydiorganosiloxane oligourea segmented copolymers with components such as tackifying resins, inorganic fillers, plasticizers or other materials essentially non-reactive with the polydiorganosiloxane polyurea segmented oligomer reactants, the materials to be blended can be added further downstream in the reactor after a substantial portion of the reaction of the diisocyanate, the polydiorganosiloxane amine, and the isocyanate functional endcapping agent has taken place. Another suitable order of addition is addition of the polydiorganosiloxane amine first, the additive second, and the diisocyanate and isocyanate functional endcapping agent third, with the diisocyanate and the endcapping agent fed in a continuous manner. If the additive can be conveyed in the reactor, it can be added into the reactor first with the polydiorganosiloxane amine, diisocyanate, and isocyanate functional endcapping agent following separately at later stages in the process.
The substantially solventless process of the present invention has several advantages over conventional solution polymerization processes for making polydiorganosiloxane oligourea segmented copolymers such as the ability to directly produce shaped articles with reduced heat histories, the ability to directly blend in fillers, tackifying resins, and other property modifiers, and the elimination of solvent. Because the polydiorganosiloxane oligourea segmented copolymers of this invention typically have low melt viscosities, they can be processed at lower temperature than can fully chain extended analogs.
In general, long exposure to heat would be expected to degrade polydiorganosiloxane oligourea segmented copolymoers and leads to a degradation of physical properties. The degradation experienced by certain solution polymerized polydiorganosiloxane oligourea segmented copolymers upon drying and subsequent hot melt extrusion is also overcome by the continuous process of the present invention because reactively extruded polydiorganosiloxane oligourea segmented copolymers can be extruded directly from the polymerization zone through a die to form shaped articles such as tubing and films without the additional heat history associated with solvent removal and the subsequent oligomer reheating.
The ability to eliminate the presence of solvent during the reaction of the diisocyanate, the endcapping agent and the optional polydiorganosiloxane di or mono amine yields a much more efficient reaction. The average residence time using the process of the present invention is typically 10 to 1000 times shorter than that required in solution polymerization. A small amount of solvent can be added, if necessary, e.g., from about 0.5% up to about 5% of the total composition, in this process either as a carrier for injecting otherwise solid materials or in order to increase stability of an otherwise low flowrate stream of material into the reaction chamber.
While the continuous solventless process for making the copolymers has many advantages over the solvent process, there may be some situations where the solvent process is preferred or where a combination of the two is preferred. In the later case, polydiorganosiloxane oligourea segmented copolymer could be made by the continuous process and subsequently mixed in solvent with thermal initiators, photoinitiators, tackifying resins, plasticizers and/or filler components.
The ability to eliminate the presence of solvent during the reaction of polyamine and polyisocyanate yields a much more efficient reaction. The average residence time using the process of the present invention is typically 10 to 1000 times shorter than that required in solution polymerization. A small amount of non-reactive solvent can be added, if necessary, for example, from about 0.5% up to about 5% of the total composition, in this process either as a carrier for injecting otherwise solid materials or in order to increase stability of an otherwise low flowrate stream of material into the reaction chamber.
This invention is further illustrated by the following examples that are not intended to limit the scope of the invention. In the examples all parts and percentages are by weight unless otherwise indicated. All molecular weights reported are number average molecular weights in grams/mol.
Titration of Polydiorganosiloxane and Organic Diamines
Multiple lots of some of the diamines were synthesized for various examples. The actual number average molecular weight of polydiorganosiloxane or organic diamines were determined by the following acid titration. Sufficient diamine to yield about 1 milliequivalent of amine is dissolved in 50/50 tetrahydrofuran/isopropyl alcohol to form a 10% solution. This solution was titrated with 1.0N hydrochloric acid with bromophenyl blue as an indicator to determine number average molecular weight The molecular weights are dependent on the exact ratio of the reactants used in the diamine synthesis and the extent of stripping cyclic siloxanes. Remaining cyclics are diluents that increase the apparent molecular weight of polydiorganosiloxane diamine.
Polydimethylsiloxane Diamine A
A mixture of 4.32 parts bis(3-aminopropyl)tetramethyl disiloxane and 95.68 parts octamethylcyclotetrasiloxane, was placed in a batch reactor and purged with nitrogen for 20 minutes. The mixture was then heated in the reactor to 150xc2x0 C. Catalyst, 100 ppm of 50% aqueous cesium hydroxide, was added and heating continued for 6 hours until the bis(3-aminopropyl) tetramethyl disiloxane had been consumed. The reaction mixture was cooled to 90xc2x0 C., neutralized with excess acetic acid in the presence of some triethylamine, and heated under high vacuum to remove cyclic siloxanes over a period of at least five hours. The material was cooled to ambient temperature, filtered to remove any cesium acetate that had formed, and titrated with 1.0N hydrochloric acid to determine number average molecular weight. Two lots were prepared and the molecular weights of Polydimethylsiloxane Diamine A were Lot 1:5280 and Lot 2:5310.
Polydimethylsiloxane Diamine B
Polydimethylsiloxane diamine was prepared as described for Polydimethylsiloxane Diamine A except 2.16 parts bis(3-aminopropyl)tetramethyl disiloxane and 97.84 parts octamethylcyclotetrasiloxane were used. Two lots were prepared. The molecular weight of Polydimethylsiloxane Diamine B was 10,700.
Polydimethylsiloxane Diamine C
A mixture of 21.75 parts Polydimethylsiloxane Diamine A and 78.25 parts octamethylcyclotetrasiloxane was placed in a batch reactor, purged with nitrogen for 20 minutes and then heated in the reactor to 150xc2x0 C. Catalyst, 100 ppm of 50% aqueous cesium hydroxide, was added and heating continued for 3 hours until equilibrium concentration of cyclic siloxanes was observed by gas chromatography. The reaction mixture was cooled to 90xc2x0 C., neutralized with excess acetic acid in the presence of some triethylamine, and heated under high vacuum to remove cyclic siloxanes over a period of at least 5 hours. The material was cooled to ambient temperature, filtered, and titrated with 1.0N hydrochloric acid to determine number average molecular weight. The molecular weight of resulting Polydimethylsiloxane Diamine C was 22,300.
Polydimethylsiloxane Diamine D
Polydimethylsiloxane diamine was prepared as described for Polydimethylsiloxane Diamine C except 12.43 parts Polydiorganosiloxane Diamine A and 87.57 parts octamethylcyclotetrasiloxane were used. Two lots were prepared. The molecular weights of the resulting Polydimethylsiloxane Diamine D were Lot 1-35,700 and Lot 2-37,800.
Polydimethylsiloxane Diamine E
Polydimethylsiloxane diamine was prepared as described for Polydimethylsiloxane Diamine C except that 8.7 parts Polydimethylsiloxane Diamine A and 91.3 parts octamethylcyclotetrasiloxane were used. The molecular weight of the thus-produced Polydimethylsiloxane Diamine E was 50,200.
Polydiphenyldimethylsiloxane Diamine F
To a 3-necked round bottom flask fit with mechanical stirrer, static nitrogen atmosphere, oil heating bath, thermometer, and reflux condenser, were added 75.1 parts octamethylcyclotetrasiloxane, 22.43 parts octaphenylcyclotetrasiloxane, and 2.48 parts bis(3-aminopropyl)tetramethyl disiloxane. Under static nitrogen atmosphere, the reactants were heated to 150xc2x0 C. and degassed under aspirator vacuum for 30 seconds before restoring static nitrogen atmosphere. A charge of 0.2 grams cesium hydroxide solution (50% aqueous) was added to the flask and heating continued for 16 hours at 150xc2x0 C. The flask was cooled to ambient temperature and then 2 mL triethylamine and 0.38 mL acetic acid were added. With good agitation flask was placed under a vacuum of 100 N/m2 (100 Pa), heated to 150xc2x0 C., and maintained at 150xc2x0 C. for 5 hours to remove volatile materials. After 5 hours heat was removed and contents cooled to ambient temperature. The molecular weight of Polydiphenyldimethylsiloxane Diamine F was 9620.
The following polydimethylsiloxane monoamines were synthesized for various examples according to the procedures of U.S. Pat. No. 5,091,483 Example 6 (terminating agent) and Example 10 (silicone monoamine). The actual number average molecular weight of the different lots are determined by acid titration.
Aminopropyldimethylfluorosilane Terminating Agent
To a 500 mL 3-necked round bottom flask was added 49.6 grams 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 29.6 grams ammonium fluoride, and 300 mL cyclohexane. While heating under reflux, water was removed by means of Dean-Stark trap. After 18 hours, 4.4 mL of water was collected, and the clear, colorless solution was transferred while warm to a 500 mL 1-neck round bottom flask. The solvent was removed on a rotary evaporator to provide 165 grams of white solid. The solid was dissolved in 200 ml methylene chloride, 30 grams of hexamethyl disilazane was added, and the mixture was stirred and heated under reflux for 5 hours. The mixture was filtered and the solvent removed under aspirator vacuum. The product was distilled (boiling point of 70xc2x0 C.) under aspirator vacuum to provide 3aminopropyldimethylfluorosilane as a clear, colorless oil. The yield was 54 grams (100%), that was determined to be pure by vapor phase chromatography. The structure was confirmed by NMR spectroscopy.
Polydimethylsiloxane Monoamine A
To 1.6 parts of 2.5 M n-butyl lithium were added 7.4 parts of octamethylcyclotetrasiloxane that had been purged with argon and the mixture was then stirred for 30 minutes; 500 parts of 50% hexamethylcyclotrisiloxane in dry tetrahydrofuran was added and the reaction mixture stirred at room temperature for 18 hours until the polymerization was complete. To the resulting viscous syrup was added 3.4 parts 3-aminopropyldimethylfluorosilane terminating agent. The viscosity rapidly decreased. After stirring for 2 hours, the solvent was distilled off on a rotary evaporator. The product was filtered to remove lithium fluoride and provided Polydimethylsiloxane Monoamine A as a clear, colorless oil. The number average molecular weight of Polydimethylsiloxane Monoamine A was 9800.
Polydimethylsiloxane Monoamine B
To 1.6 parts of 2.5 M n-butyl lithium were added 7.4 parts of octamethylcyclotetrasiloxane that had been purged with argon and the mixture was then stirred for 30 minutes; 1000 parts of 50% hexamethylcyclotrisiloxane in dry tetrahydrofuran was added and the reaction mixture stirred at room temperature for 18 hours until polymerization was complete. To the resulting viscous syrup was added 3.4 parts 3-aminopropyldimethylfluorosilane terminating agent. The viscosity rapidly decreased. After stirring for 2 hours, the solvent was distilled off on a rotary evaporator. The product was filtered to remove lithium fluoride and provided 500 Polydimethylsiloxane Monoamine B as a clear, colorless oil. The number average molecular weight was 20,600.
Polydimethylsiloxane Monoamine C
To 588 grams (2.64 mol) hexamethylcyclotrisiloxane which had been degassed via boiling then cooled to room temperature was added 500 mL dry tetrahydrofuran. To this solution was added 19.3 mL (0.05 mol) of 2.59 M n-butyl lithium and the reaction mixture stirred at room temperature for 6.5 hours until the polymerization was complete. To the resulting viscous syrup was added 23.2 mL (0.06 mol) of 2.58M 3-aminopropyldimethyl fluorosilane terminating agent. After stirring overnight the solvent and remaining hexamethylcyclotrisiloxane were distilled off on a rotary evaporator to afford the Polydimethylsiloxane Monoamine C as a clear, colorless oil. The number average molecular weight of Polydimethylsiloxane Monoamine C was 12,121.
The following test methods were used to characterize the polydiorganosiloxane oligourea segmented copolymers produced in the following examples:
Characterization of Uncured Samples
Rheological properties of the uncured materials were determined using Rheometrics, RDA II Rheometer using dynamic temperature ramp mode (xe2x88x9230xc2x0 C.-175xc2x0 C.) at a ramp rate of 5xc2x0 C., 25 mm parallel plates, a strain of 2.0% and a frequency of 10.0 rad/s. Sample thickness was 1-2 mm.
The storage modulus, Gxe2x80x2, represents that portion of the mechanical energy that is stored, i.e., completely recoverable, when the viscoelastic material undergoes cyclic deformation. The stored energy is analogous to that seen in a simple spring going through cyclic deformation.
The loss modulus, Gxe2x80x3, represents that portion of the mechanical energy dissipated, i.e., converted to heat, when the viscoelastic material undergoes cyclic deformation. The dissipated energy is analogous to that seen in a simple dashpot going through cyclic deformation.
Stress Rheometer, Rheometrics, DSR, was used to characterize shear creep viscosities of the uncured materials in step stress (creep) mode with 25 mm parallel plates.
Characterization of Cured Samples
Free-radically curable materials were squeezed between two polyester films to a thickness of approximately 1 mm and cured at an intensity of 1.73 mW for a given length of time with low intensity ultraviolet lights. Mechanical properties of the cured samples were characterized as follows:
Mechanical testing was performed on an Instron Model 1122 tensile tester. Testing was performed according to a modification of ASTM D412-83. Samples were prepared according to Method B (cut ring specimens). Type 1 rings (5.1 cm circumference) were produced with a specially-designed precision ring cutter. The Instron analog output signal was routed to a digital voltmeter with accuracy better than 0.5 percent and the digital readings were recorded by a computer. Modifications to the ASTM were as follows:
1. The crosshead speed was 12.7 cm/min rather than 50.8 cm/min.
2. The test fixture shafts (upper and lower jaw) both rotated at 30 RPM in the same direction in order to maintain uniform strain throughout the entire ring.
3. The thickness of the rings was 1 mm.
Molecular Weight
The weight average and number average molecular weights of selected polydimethylsiloxane oligourea segmented copolymers were determined via gel permeation chromatography with a HP 1090 Chromatograph equipped with a HP 1037 A Refractive Index detector, a Waters 590 pump, a Waters Wisp auto-injector, and a Kariba column oven at R.T. The copolymer was dissolved in DMF w/v 0.05% LiBr at 15 mg/5 mL, filtered with a 0.2 micron nylon filter, and 100 microliters injected into a Jordi Mixed Bed column. The elution rate was 0.5 mL/min in DMF+0.05% w/v LiBr. Calibration was based on Polystyrene standards from Pressure Chemical Company, Pittsburgh, Pa. thus reported molecular weights are the Polystyrene equivalents.